Also, outside of FFL03/FFL01 holders I don't believe any out of state resident can purchase a firearm and complete the NICS (or in our case DROS) in a different state of their residency.

Unlicensed (non-FFL) out of state residents can acquire firearms while in a different State, but only rifles and shotguns and only from an FFL and only at the FFL's licensed premises and only if the transaction complies with the laws of both States.

So the OP's example is not possible for two reasons. First, the firearm is not a rifle or shotgun. Second, there's no way for the buyer to comply with California's laws without a California DL/ID or military ID with orders.

Unlicensed (non-FFL) out of state residents can acquire firearms while in a different State, but only rifles and shotguns and only from an FFL and only at the FFL's licensed premises and only if the transaction complies with the laws of both States.

So the OP's example is not possible for two reasons. First, the firearm is not a rifle or shotgun. Second, there's no way for the buyer to comply with California's laws without a California DL/ID or military ID with orders.